Coater with applicator rods

ABSTRACT

A device for applying coating material to the surface of a moving web of material such as paper or the like wherein a drum is rotatably mounted to have a portion thereof pass beneath the surface of a coating fluid bath and to have a portion thereof extend above the fluid bath. The coating drum has a series of rod-like members disposed longitudinally along the outer surface thereof. The rod-like members have a diameter which is substantially less than the diameter of the cylindrical drum and are arranged to pass beneath the coating fluid bath and to carry fluid above the surface of the bath into contact with the moving web. The web of material rides against the outer surface of the rod-like members and is coated uniformly as the cylindrical drum is rotated.

United States Patent Mahoney 1 Mar. 21, 197 2 54 COATER WITH APPLICATOR RODS 2,128,516 8/1938' Graham ..118/246 x [72] imam" Ralph Mammy s/i3?) i ii li fi: ..1 18/246 [73] Assignee: Beloit Corporation, Beloit, Wis.

Primary Examiner-John F. McIntosh [221 Fled: 1970 Attorney-Hill, Sherman, Meroni, Gross & Simpson [21] App]. No.: 80,808

[57] ABSTRACT Related Application Dam A device for applying coating material to the surface of a mov- 3 C i i f Sen 775 4 Nov 13, 1968 ing web of material such as paper or the like wherein a drum is abandoned rotatably mounted to have a portion thereof pass beneath the surface of a coating fluid bath and to have a portion thereof 52 ug 24 11 3 202 extend above the fluid bath. The coating drum has a series of [5 1] Int. Cl ..B05c 1/12 rod'like members disposed longitudinally along the Outer 58 Field of Search ..1 18/212, 63, 246, 216, 221, face thereof- The rod-like members have a diameter which is 222 2 2 DIG 7; 202 20 substantially less than the diameter Of the cylindrical drum and are arranged to pass beneath the coating fluid bath and to l 56] References Cited carry fluid above the surface of the bath into contact with the moving web. The web of material rides against the outer sur- UNITED STATES PATENTS face of the rod-like members and is coated uniformly as the cylindrical drum is rotated. 30,788 11/1860 Martin ..118/246 1,575,868 3/1926 Roles ..118/246 X 5 Claims, 1 Drawing Figure COATER WITH APPLICATOR RODS This application is a continuation of Ser. No. 775,466, filed Nov. 13, 1968, now abandoned.

BACKGROUND OF THE INVENTION 1. Description of the Prior Art Considerable inventive effort and attention has been directed to developing means for satisfactorily applying a uniform layer of coating fluid to the surface of a rapidly moving web. Such prior art methods include the use of an applicator roll which rotates partially submerged in a fluid tank and which carries coating fluid to the surface of the web. The web then passes through squeezing rolls or the like to remove excess fluid therefrom. Other prior art devices include the combination of an applicator roll and a roll to remove excess material directly. For instance, in US. Pat. No. 2,874,674 a coating applicator roll is provided to direct fluid against the surface of a web and simultaneously create nip pressure between the applicator roll and a platen roll.

Still other prior art techniques involve applying a substantial excess of fluid to the surface of the web and then utilizing a doctor blade to scrape the excess coating from the surface of the web. An entire field of prior art has been developed which is directed to techniques for utilizing a doctor blade to remove excess coating from the traveling web. For instance, the doctor blade may either be in contact with the web or spaced slightly from the moving surface. Other devices use an airknife as is well understood in the art for removing and smoothing the coating material after having been applied to the surface ofthe moving web.

Still other devices have been developed which utilize an applicator roll and an adjacent roll wherein the applicator roll is spaced slightly from the adjacent or back-up roll and wherein the rotation of the applicator roll develops a hydraulicpressure at the surface of the web for uniformly applying the coating material thereto.

2. Field of the Invention The field of art to which this invention pertains is devices for applying a uniform coating of fluid to the surface of a moving web and in particular to means for applying the fluid by utilizing a rotating partially submerged applicator drum.

SUMMARY OF THE INVENTION It is an important feature of the present invention to provide a means for applying a coating material to the surface of a moving web.

It is another feature of the present invention to provide an improved rotating drum structure for uniformly applying coating fluid to the adjacent surface of a traveling web.

It is also an object of the present invention to provide an applicator roll having a series of protuberances or projections along the surface thereof for trapping coating fluid beneath the surface of a coating fluid bath and for lifting the coating fluid from the surface of the bath to points upwardly thereof for application to the surface of a traveling web.

It is an additional object of the present invention to provide a coating device which includes a cylindrical drum applicator roll having a number of rod-like members disposed longitudinally along the outside surface of the drum and wherein the rod-like members trap coating fluid when they are submersed beneath the level of a coating fluid bath and carry the fluid from the bath to points upwardly thereof for being applied to the surface of a moving web.

It is also an object of the present invention to provide an applicator roll for a coating device wherein the applicator roll has a series of cylindrical rods disposed longitudinally and spaced uniformly along the surface thereof and wherein the cylindrical rods have a diameter which is substantially less than the diameter of the applicator roll such that rotation of the applicator roll into a coating fluid bath causes coating fluid to be trapped between the surface of the applicator roll and the cylindrical rods and carried upwardly thereof for being moved into contact with the adjacent surface of a traveling web.

It is a further object of the present invention to provide a coating system for applying a uniform coating of fluid to both surfaces of a traveling web in combination with means for smoothing the excess fluid after having been applied to the web by an applicator drum, the applicator drum having uniformly spaced cylindrical rods at the surface thereof.

These and other objects, features and advantages of the present invention will be understood in further detail from the following description and the associated drawings wherein reference numerals are utilized to designate a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWING The single drawing of the present application is a diagrammatic illustration of an applicator roll according to the present invention and showing a traveling web as it is engaged against the surface of separate applicator rolls in such a manner as to uniformly apply coating fluid to both sides of the traveling web. The drawing illustrates in detail the orientation of the rod-like members which are disposed uniformly at the surface of the applicator roll and shows the applicator roll immersed in a fluid bath and also indicates generally the relative difference in size between the diameter of the rods which are disposed along the surface of the applicator roll and of the applicator roll itself.

DESCRIPTION OF THE PREFERRED EMBODIMENT The apparatus shown in the single drawing of the present application provides a means for applying a uniform layer of coating material to the surface of a moving web.

Coatings are applied to paper and related web materials for such reasons as improving the ability to print on the surface of the paper, improving the gloss of the paper, smoothing, increasing the opacity, brightness, and the like. Such coatings generally consist of a pigment or series of pigments mixed with an adhesive.

' Coatings may include such pigments as barium sulphate, calcium carbonate, calcium silicate, clay, satin white, diatomaeceous silica, talc, titanium and adhesives including for example the natural proteins, i.e., casein and soya, animal glue; starch; and the like. Various pigments and adhesives may be mixed together to achieve a particular coating condition. Other ingredients may also be mixed with the solution such as setting agents, defoamers, waxes or the like. Coatings may be applied in a number of layers and the preparation and use of coatings in general are well known in the art.

A traveling web may be coated on or off a paper making machine and various methods and devices have been developed for applying coatings to the webs. For instance, trailing blade coaters or doctor blades, air-knife coaters, roll coaters, dip coaters, brush coaters, spray. coaters, print coaters, strip coaters and the like. Many variations in coating processes in the design of coating apparatus are well known in the art. Coating of paper, plastic webs and the like is such an important process in the making of the web material that it has inspired an entire field of art and numerous inventions related to coating techniques and apparatus.

The coating device shown in the drawing provides for the smoothing of a uniform layer of coating material upon a portion of a flexible web or sheet which is traveling against the surface of a coating applicator. The invention is applicable to the coating of woven or felted fabrics, paper, sheets of rubber or other resinous material, cellulose films, and other sheet material of similar nature.

Referring specifically to the drawing, a coating pan 10 is used to contain a bath of coating fluid 11. The coating pan 10 may be an elongated pan for supporting the bath of coating fluid along the entire length of a roll. The web which is moved against the roll may be of a considerable width, and the device of the present invention provides a means for uniformly applying coating fluid from the bath 11 across the entire width of the traveling web.

The coating fluid may be any one of the above mentioned type fluids and may be of varying viscosities depending on the type of web material being coated and depending upon the requirements of the coating process.

The coating pan is shown diagrammatically only in the drawing and takes the form of a rectangular or U-shaped cross sectional, tub. However, the coating pan 10 may assume a more sophisticated form as is well understood in the art so long as coating fluid is maintained in sufficient quantities against the lower surface of the coating applicator and so long as a sufficient supply of coating fluid is continuously available to the coating pan.

A web of material to which is being applied the coating fluid of the present invention is indicated generally by the reference numeral 12 and may extend from a previous paper machine stage to the starting point shown in the drawing, and may proceed from the terminal point shown in the drawing to further operational stages such as for instance polishing stages or the like.

The web of material passes beneath a first roller 13 and is guided over the coating applicator to a second roller 14. From the roller 14 the web moves to an applicator device for coating the reverse side of the web.

The applicator device utilized for coating the first side of the web includes a cylindrical coating drum 15. The drum is rotatably mounted to have a lower portion 16 thereof extended generally into and beneath the fluid bath 11. The upper portion 17 of the drum extends above the fluid bath in the general direction of the moving web 12. Only the cross sectional view of the cylindrical drum 15 is shown in the drawing, however, it is understood that the drum 15 may be an elongated roll extending at least the entire length of the web 12.

Applicator rolls have been used in prior art coating applicators. Nevertheless, a continuous effort has been made to improve applicator rolls for applying a more uniform coating of the desired fluid to the surface of a web which may be traveling at substantial speeds.

The applicator roll of the present invention, rather than 1 have the cylindrical surface thereof contact the surface of the web directly, has a series of protuberances 18 which are disposed along the length of the cylindrical drum 15. The protuberances 18 take the form of rod-like members or projections which are disposed substantially uniformly around the cross sectional periphery of the cylindrical applicator roll and which have their axes disposed substantially parallel to the axis of the drum 15.

The rod-like members 18 have a generally circular cross section and have a diameter which is substantially less than the diameter of the applicator drum 15.

As the drum 15 is rotated, the rod-like members are carried beneath the surface of the coating fluid bath l1 and are then moved from beneath the surface to points above the surface. Coating fluid is trapped in cavities such as is shown in the areas 19 and 20. Fluid which is trapped between the adjacent rod-like members is carried upwardly and is transferred against the lower surface of the traveling web 12. The generally circular cross section of the rod'like members 18 allows excess fluid to flow smoothly therefrom as the individual rods contact the surface of the traveling web.

As the web passes against the surface of the applicator roll, fluid from the coating pan is applied thereto, and the web passes to the roll 14 which is disposed immediately adjacent to an air-knife 21. It is known that such an air-knife provides means to apply a substantially non-divergent jet of air emitted from a straight slit orifice of a nozzle to the coating on the web and tends to leave a uniformly thick layer of coating thereon. in practice, the jet of air issues from the nozzle with substantially uniform velocity throughout its entire extent and impinges upon the web coating at an angle and in a direction opposite to the direction of web travel, thereby cutting away the excess coating and leaving the desired quantity of coating on the web in a layer of uniform thickness. The outlet portion of the air-knife 21 is indicated generally by a slit or opening 22.

The air-knife generates a mist or stream of coating fluid immediately adjacent the traveling web, and aco'ntainer 23 may be utilized to receive excess coating or mist generated by the action of the air-knife 21.

The web of material passes against a further roller 24 and extends against the outer surface of a further applicator roll 25. The applicator roll 25 is substantially identical to the applicator roll 15, and is partially submersed in a coating fluid pan 26 as shown. As can be seen, the cylindrical coating applicator 15 applied coating material from the fluid bath 1 l to a first surface 27 of the moving web 12, while the drum 25 applies coating material from a fluid bath 28 to a second surface 29 of the traveling web.

Similar to the air-knife 21, an air-knife 30 is positioned beneath the traveling web 12 and directs an air stream in a direction opposite to the direction of movement of the web for smoothing excess material therefrom.

The web may then be moved from the air-knife area to a drier 31 such as an infrared drier or the like. In this way, the coating material applied to the web is dried and hardened, and the web is then ready for a further operational stage such as a polishing stage or the like.

1 claim as my invention:

1. in an apparatus for processing a continuously traveling web, a device for applying a coating of fluid to the surface of the web comprising:

a coater pan for holding a bath of coating fluid to be applied to the web surface,

a cylindrical drum rotatably mounted in such relation to said coater pan as to have a portion thereof continuously submerged beneath the surface of the coating fluid bath,

a series of rod-like members each having an outer cylindrical surface,

the rod-like members being mounted on the surface of the drum so that their cylindrical outer surface meets the cylindrical outer surface of the drum in line contact forming coating retaining pockets beneath each of the rod-like members facing radially inwardly toward the drum surface so that the under surface of the rod-like member holds the coating inwardly against centrifugal force due to rotation of the drum.

2. An apparatus as defined in claim 1 wherein the rod-like members are spaced uniformly around the periphery of the cylindrical drum and extend longitudinally of the drum in a direction generally parallel to the axis thereof.

3. An apparatus as defined in claim 1 wherein the rod-like members have a substantially circular cross section.

4. An apparatus as defined in claim 1 wherein the diameter of the rod-like members is substantially less than the diameter of the cylindrical drum.

5. An apparatus as defined in claim 4 wherein the rod-like members are spaced apart a distance greater the diameter of the rod-like members. 

1. In an apparatus for processing a continuously traveling web, a device for applying a coating of fluid to the surface of the web comprising: a coater pan for holding a bath of coating fluid to be applied to the web surface, a cylindrical drum rotatably mounted in such relation to said coater pan as to have a portion thereof continuously submerged beneath the surface of the coating fluid bath, a series of rod-like members each having an outer cylindrical surface, the rod-like members being mounted on the surface of the drum so that their cylindrical outer surface meets the cylindrical outer surface of the drum in line contact forming coating retaining pockets beneath each of the rod-like members facing radially inwardly toward the drum surface so that the under surface of the rod-like member holds the coating inwardly against centrifugal force due to rotation of the drum.
 2. An apparatus as defined in claim 1 wherein the rod-like members are spaced uniformly around the periphery of the cylindrical drum and extend longitudinally of the drum in a direction generally parallel to the axis thereof.
 3. An apparatus As defined in claim 1 wherein the rod-like members have a substantially circular cross section.
 4. An apparatus as defined in claim 1 wherein the diameter of the rod-like members is substantially less than the diameter of the cylindrical drum.
 5. An apparatus as defined in claim 4 wherein the rod-like members are spaced apart a distance greater the diameter of the rod-like members. 